/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.zookeeper.server;

import java.io.IOException;
import java.util.HashSet;
import java.util.Set;

import org.apache.jute.InputArchive;
import org.apache.jute.OutputArchive;
import org.apache.jute.Record;
import org.apache.zookeeper.data.Stat;
import org.apache.zookeeper.data.StatPersisted;

/**
 * This class contains the data for a node in the data tree.
 * <p>
 * A data node contains a reference to its parent, a byte array as its data, an
 * array of ACLs, a stat object, and a set of its children's paths.
 * 
 */
public class DataNode implements Record {
	/**
	 * the acl map long for this datanode. the datatree has the map
	 */
	Long acl;

	/**
	 * the list of children for this node. note that the list of children string
	 * does not contain the parent path -- just the last part of the path. This
	 * should be synchronized on except deserializing (for speed up issues).
	 */
	private Set<String> children = null;

	/** the data for this datanode */
	byte data[];

	/** the parent of this datanode */
	DataNode parent;

	/**
	 * the stat for this node that is persisted to disk.
	 */
	public StatPersisted stat;

	/**
	 * default constructor for the datanode
	 */
	DataNode() {
		// default constructor
	}

	/**
	 * create a DataNode with parent, data, acls and stat
	 * 
	 * @param parent the parent of this DataNode
	 * @param data   the data to be set
	 * @param acl    the acls for this node
	 * @param stat   the stat for this node.
	 */
	public DataNode(DataNode parent, byte data[], Long acl, StatPersisted stat) {
		this.parent = parent;
		this.data = data;
		this.acl = acl;
		this.stat = stat;
	}

	/**
	 * Method that inserts a child into the children set
	 * 
	 * @param child to be inserted
	 * @return true if this set did not already contain the specified element
	 */
	public synchronized boolean addChild(String child) {
		if (children == null) {
			// let's be conservative on the typical number of children
			children = new HashSet<String>(8);
		}
		return children.add(child);
	}

	synchronized public void copyStat(Stat to) {
		to.setAversion(stat.getAversion());
		to.setCtime(stat.getCtime());
		to.setCzxid(stat.getCzxid());
		to.setMtime(stat.getMtime());
		to.setMzxid(stat.getMzxid());
		to.setPzxid(stat.getPzxid());
		to.setVersion(stat.getVersion());
		to.setEphemeralOwner(stat.getEphemeralOwner());
		to.setDataLength(data == null ? 0 : data.length);
		int numChildren = 0;
		if (this.children != null) {
			numChildren = children.size();
		}
		// when we do the Cversion we need to translate from the count of the creates
		// to the count of the changes (v3 semantics)
		// for every create there is a delete except for the children still present
		to.setCversion(stat.getCversion() * 2 - numChildren);
		to.setNumChildren(numChildren);
	}

	synchronized public void deserialize(InputArchive archive, String tag) throws IOException {
		archive.startRecord("node");
		data = archive.readBuffer("data");
		acl = archive.readLong("acl");
		stat = new StatPersisted();
		stat.deserialize(archive, "statpersisted");
		archive.endRecord("node");
	}

	/**
	 * convenience methods to get the children
	 * 
	 * @return the children of this datanode
	 */
	public synchronized Set<String> getChildren() {
		return children;
	}

	/**
	 * Method that removes a child from the children set
	 * 
	 * @param child
	 * @return true if this set contained the specified element
	 */
	public synchronized boolean removeChild(String child) {
		if (children == null) {
			return false;
		}
		return children.remove(child);
	}

	synchronized public void serialize(OutputArchive archive, String tag) throws IOException {
		archive.startRecord(this, "node");
		archive.writeBuffer(data, "data");
		archive.writeLong(acl, "acl");
		stat.serialize(archive, "statpersisted");
		archive.endRecord(this, "node");
	}

	/**
	 * convenience method for setting the children for this datanode
	 * 
	 * @param children
	 */
	public synchronized void setChildren(HashSet<String> children) {
		this.children = children;
	}
}
